CN101479229A - Process for converting nitrile compounds to carboxylic acids and corresponding esters - Google Patents

Abstract

The present invention relates to a process for converting hydrocarbon-based compounds comprising at least one nitrile function to compounds comprising at least one carboxylic function, and also to a process for obtaining ester compounds from the resulting carboxylic compounds. The process comprises reacting the nitrile compound with a basic hydroxyl compound in solution in a solvent at a temperature of 80 to 200 DEG C, removing the ammonia formed, reacting the resulting salt with an inorganic acid and then recovering the compound comprising at least one carboxylic function and, optionally, esterifying the resulting acids by reacting same with an alcohol.

Description

Method for converting nitrile compounds into carboxylic acids and corresponding esters

technical field

The present invention relates to a process for the conversion of compose hydrocarbons containing at least one nitrile function into compounds containing at least one carboxyl function, and to a process for obtaining esters from the carboxyl compounds thus obtained.

The present invention relates more particularly to dinitrile compounds obtained as products and by-products in the hydrocyanation of butadiene, such as from methyl-glutaronitrile, ethyl-succinonitrile, and optionally adiponitrile or A method of converting a mixture of these three compounds into a diacid compound on the one hand and a diester compound on the other hand.

Background technique

The preparation of adiponitrile by hydrocyanation of butadiene has been developed industrially for decades. The process has a high selectivity for adiponitrile, an important chemical intermediate for the synthesis of hexamethylenediamine or caprolactam and for the preparation of polyamides.

However, this process also produces branched dinitrile compounds, such as methyl-glutaronitrile, ethyl-succinonitrile, which are separated and recovered in particular by distillation.

In general, the above recovery of branched dinitrile compounds produces a mixture containing primarily methyl-glutaronitrile with incidental ethyl-succinonitrile and adiponitrile.

Various schemes have been proposed for adding value to these by-products or mixtures. One of these methods consists in the hydrogenation of dinitrile compounds to primary amines, in particular for the production of methylpentamethylenediamine (MPMD), which is used as a monomer for the preparation of specialty polyamides. The process requires either a purification step of methyl-glutaronitrile or a purification step of methylpentamethylenediamine.

In industry, the above-mentioned by-products are usually destroyed by combustion, which is value-added in the form of steam and energy, but is accompanied by the generation of gaseous emissions containing _CO2 and nitrogen oxides.

Therefore, there is a need and a demand to find new value-added routes by converting the above-mentioned dinitrile compounds or mixtures thereof into value-addable and economically beneficial compounds.

Contents of the invention

One of the objects of the present invention is in particular to propose a process which, on the one hand, makes it possible to convert the above-mentioned dinitrile compounds into carboxyl compounds which are used in particular as chemical intermediates, for example for the preparation of polyurethanes and polyamides. The monomers, or alternatively, are converted into diester compounds, which are used in particular as solvents.

For this purpose, the invention proposes a process for converting a compound containing at least one nitrile function into a compound containing at least one carboxyl group, which consists in bringing the nitrile compound together with a hydroxyl basic compound in solution in a solvent at a temperature between 80° C. The reaction is carried out at a temperature of up to 200°C, preferably between 80°C and 150°C, the ammonia formed is removed, the resulting salt is reacted with a mineral acid, and the compound containing at least one carboxyl group is recovered.

According to a preferred feature of the present invention, the hydroxy basic compound is an alkali metal hydroxide, such as sodium hydroxide, potassium hydroxide and the like. Advantageously, aqueous solutions of the abovementioned hydroxyl basic compounds are used. The concentration of the basic compound in the aqueous solution is advantageously between 5 and 30% by weight.

According to another advantageous feature of the invention, the hydroxy basic compound is used in an excess of 3-20%, advantageously 3-10%, relative to the stoichiometric amount required for converting the nitrile function into the carboxyl function.

The reaction is carried out either at atmospheric pressure, advantageously at a temperature at which the solvent (such as water) is refluxed, or under pressure, while removing the ammonia formed or without removing said ammonia formed which is at least partially dissolved in the reaction medium. Ammonia ammonia.

According to one embodiment of the invention, the method is carried out continuously. The reaction with basic compounds can be carried out in a single piston reactor (réacteur piston) or in a plurality of stirred reactors (réacteurs agités) arranged in series. The reaction is advantageously carried out in an apparatus comprising two consecutive and separate reaction zones, the first of which operates in agitation (en regime agité), followed by the second zone (en régime piston) in operation. The presence of the above two reaction zones allows for the complete conversion of nitrile functions into carboxyl functions. This complete conversion facilitates the recovery and isolation of the aforementioned carboxyl compounds, especially when the nitrile compound to be converted is a dinitrile compound, and thus avoids the presence of cyano compounds and/or amides in the final reaction medium. In this way, the process can be carried out in a plant comprising a stirred reactor equipped with a condenser for obtaining reflux and a device for recovering the ammonia formed, and a piston reactor installed in series with the stirred reactor device. The stirred reactor can also be operated under pressure without separation of the formed ammonia dissolved in the reaction medium.

The first stirred reactor may advantageously be a loop reactor comprising an inner circulation loop and an outer circulation loop, on which a heat exchanger is advantageously provided.

Of course, other types of stirred reactors can also be used.

Advantageously, the temperature and pressure can be different in stirred reactors and piston reactors. Piston reactors advantageously work adiabatically. Preferably, the reaction temperature in the piston reactor is higher than in the stirred reactor. Thus, the temperature in the piston reactor is advantageously higher than 100°C, preferably between 100°C and 200°C.

In the case of a discontinuous process, the operating conditions of the reactor are determined to advantageously obtain a 100% conversion of the nitrile function.

The reaction medium at the outlet of the reaction step (especially at the outlet of the piston reactor) contains carboxylate compounds of metal elements introduced with basic compounds, which are advantageously sodium carboxylates and potassium carboxylates, and the formation and dissolved ammonia.

The reaction medium described above is fed to a step where the ammonia formed can be separated, for example, in a fractionation column or a flash column.

The ammonia recovered in this way is directly valorizable or can be purified (for example by fractional distillation) in order to separate off the water and to obtain ammonia which is valorizable in the production of nitric acid and hydrocyanic acid, for example.

According to one feature of the invention, the reaction medium is subsequently acidified by adding a mineral acid in order to obtain the carboxyl compound in protonated form, also referred to hereinafter as carboxylic acid.

As inorganic acids suitable for use in the present invention, mention may be made of sulfuric acid, hydrochloric acid, organic acids having a pKa of 3 or less and mixtures thereof.

Optionally, in order to avoid the precipitation of salts, it is advantageous to add water to the reaction medium before adding the mineral acid. The amount of water added is determined so that the concentration of the salt in the reaction medium approximates the saturation concentration of the salt in water.

The abovementioned acidification is carried out in any type of reactor, especially in a stirred reactor or in-line reactor (en ligne), or in a tubular reactor with static mixer.

The amount of acid added is advantageously approximately equal to the amount required to neutralize the basic compound added in the first step.

Thereafter, the reaction medium is treated to recover the aforementioned carboxylic acid. The reaction medium can be concentrated by evaporating water and the salts are separated by filtration.

As a treatment method suitable for the present invention, liquid/liquid extraction of the above-mentioned carboxylic acids with a water-immiscible solvent is preferred.

As extraction solvents suitable for use in the present invention, water-insoluble polar solvents such as ketones, ethers and esters may be mentioned. As suitable solvents, there may be mentioned methyl isobutyl ketone, diisopropyl ether, methyl t-butyl ether, ethyl acetate, isopropyl acetate, butyl acetate, diester solvents and the like.

The aforementioned carboxylic acids are recovered in the phase containing the extraction solvent and are advantageously separated from the solvent by distillation of the solvent. Thus, solvents which form heterogeneous azeotropes with water and thus carry away the water contained in the extract phase are preferred. Therefore, the diacid recovered at the bottom of the separation column where the solvent is extracted contains no water or only a very small amount of water. The extraction solvent is advantageously recovered in the extraction step after separation of the water, for example by decantation.

According to another feature of the invention, it is possible to subject the aqueous phase recovered after extraction of carboxylic acids (which also contains salts of inorganic acids) to stripping in order to recover and extract traces of the extracted solvent.

In one embodiment of the invention, the carboxylic acid thus obtained is purified by usual techniques, ie crystallization, distillation, purification, etc.

In this way, the recovered carboxylic acid is advantageously subjected to distillation in one or more columns in order to remove light components on the one hand and heavy products on the other hand. This purification is simplified if the starting nitriles (in particular methylglutaronitrile) are purified by separation of volatile compounds such as cresols and/or pentenenitriles. The aforementioned purification is likewise facilitated if the concentration of ammonia in the acid to be purified is low, which thus limits the formation of salts, such as ammonium sulfate.

The carboxylic acids may advantageously be treated with carbon black or subjected to hydrogenation, or any other customary purification treatment, before purification by distillation, crystallization or refinement. The above purification treatment can be performed using a solution of carboxylic acid in an extraction solvent.

After purification, the recovered carboxylic acid is mis en forme to be available for other methods. As shaping methods, mention may be made of flaking, granulation or extrusion into rods.

Where the nitriles consist of by-products from the hydrocyanation of the butadiene (i.e. methyl-glutaronitrile or a mixture of methyl-glutaronitrile, ethyl-succinonitrile and adiponitrile) In this case, the recovered carboxylic acid is either methylglutaric acid or a mixture of methylglutaric acid, ethyl-succinic acid and adipic acid. The above-mentioned diacids can have various uses, in particular as monomers or co-monomers for the preparation of polyamides, polyesters, polyurethanes or as additives.

According to another embodiment of the invention, the carboxylic acid recovered after separation of the extraction solvent is used for the preparation of the diester. This embodiment is of particular interest when the aforementioned carboxylic acid originates from the conversion of the products resulting from the hydrocyanation of butadiene (in particular a mixture of methylglutaronitrile, ethylsuccinonitrile, adiponitrile). In this case, the resulting product is a diester and is generally referred to herein as a "diester".

To prepare the above-mentioned diesters, the recovered diacids, either before or after being purified, are mixed with ethanol. The esterification reaction is carried out by heating the mixture in the presence of an acidic compound for catalyzing the reaction.

Thus, the reaction can be carried out by passing through the sulfonic acid resin at a temperature between 40°C and 100°C. The medium from the column containing the resin is then distilled to separate unreacted ethanol and water produced.

The reaction can also be carried out in a reactive distillation column capable of carrying out the esterification reaction while withdrawing the water produced by the distillation. Therefore, the equilibrium can be shifted so as to obtain a conversion close to 100%.

Suitable alcohols are, for example, branched or unbranched, cyclic or acyclic aliphatic alcohols, which may contain aromatic rings and may contain 1 to 20 carbon atoms. As preferred examples, mention may be made of the following alcohols: methanol, propanol, isopropanol, benzyl alcohol, ethanol, n-butanol, isobutanol, cyclohexanol, hexanol, isooctyl alcohol, 2-ethylhexanol , pentanol, methyl-butanol, etc.

)步骤和除去尾馏分(equeutage)步骤的装置中进行蒸馏。该蒸馏可在单个塔中进行，同时二酯以中间馏分形式进行回收。The diester-containing medium is then advantageously included after removal of the heads (

) step and remove the tail fraction (equeutage) step in the device for distillation. This distillation can be carried out in a single column with the diester recovered as a middle distillate.

Advantageously, the recovered heavy fraction contains monoester compounds which are at least partially recovered and recycled during the esterification step. The diesters thus obtained can be used in various applications, such as as solvents in paints, varnishes, laques, in the surface coating industry or any other product (e.g. cable) industry, in the ink industry, in the textile industry Lubricants industry, binders and resins for sand cores of foundry moulds, cleaning products, cosmetic preparations. They can also be used as starting materials for certain chemical reactions in compositions for treating soil and plants.

More generally, they can be used alone or in formulations as cleaning, scrubbing, degreasing solvents in any industrial or domestic activity.

The diesters mentioned above are also useful as plasticizers for certain plastic materials or as monomers for the preparation of polymers.

Further advantages of the invention will become more apparent in detail with the aid of the following merely illustrative examples.

Detailed ways

Alkaline Hydrolysis of Dinitrile Compounds

To 560 g of a 15% aqueous solution of sodium hydroxide previously heated to 80° C., 108 g of a mixture of dinitrile compounds from the process of preparing adiponitrile by hydrocyanating butadiene were added within 30 min under stirring.

Described dinitrile mixture has following weight composition:

Methylglutaronitrile (MGN): 84.2%

Ethylsuccinonitrile (ESN): 11%

Adiponitrile (AdN): 4%

The balance to 100% corresponds to the various impurities with no nitrile function.

Then, the mixture was heated to obtain reflux and the mixture was maintained at this temperature for about 7 h.

The released ammonia is recovered and captured.

The progress of the reaction was controlled by potentiometric measurement (dosage potentiométrique) of hydrochloric acid solution. This assay can measure the amount of remaining sodium hydroxide, the amount of dissolved ammonia, and the amount of salified carboxyl functions corresponding to each pH jump observed during the assay.

The hydrolysis yield is given by:

RR%=V _COONa ×100/(V _NaOH +V _COONa )×NaOHi/MGNi

in:

V _COONa : corresponding to the volume of HCl solution required for neutralizing the carboxyl group forming a salt;

V _NaOH : corresponding to the volume of HCl solution required to neutralize residual sodium hydroxide;

NaOHi: corresponding to the number of moles of starting NaOH;

MGNi: the number of moles corresponding to the starting dinitrile compound;

RR: conversion rate of dinitrile compound into carboxylic acid.

The reaction is considered to be complete when the RR% approaches 100%.

The reaction medium is then cooled to room temperature, 80 g of water are added and then 105 g of 98% concentrated sulfuric acid are poured in. The pH of the aqueous solution is about 3.

Then, the aqueous phase was extracted with 3×200 ml MTBE (methyl tert-butyl ether) at 40°C. The organic phases are combined and MTBE is distilled off. 141.6 g of the diacid were obtained, the purity of which was determined potentiometrically to be about 98.5%.

Esterification

141.6 g of crude diacid were dissolved in 621 g of methanol. This solution was then placed in a round bottom flask containing 115 g of a sulfonic acid resin (sold under the trade name Amberlyst 36 DRY by Rhom et Haas) previously washed with methanol.

All reactants were boiled for 6h.

Acid functionality was determined by potentiometry with sodium hydroxide and showed a conversion of 95%.

After cooling, the above resin was isolated by filtration and washed 3 times with 150 ml of methanol. The different methanol phases were combined.

Methanol and water formed during esterification are separated by distillation.

The crude diester is then distilled in a packed column at 105° C. and 20 mbar. A diester yield of 93% was obtained with a purity of over 99% as determined by chromatographic analysis.

Claims (25)

1, will contain the method that the functional compound of at least one nitrile is converted into the compound that contains at least one carboxyl-functional, it is characterized in that this method comprises:

Described nitrile compound and hydroxyl basic cpd when existing, solvent are reacted under 80 ℃ to 200 ℃ temperature;

From reaction medium, remove the ammonia of generation;

Make and generate salt and inorganic acid reaction; With

Separate carboxylic acid cpd.

2, method according to claim 1 is characterized in that aforesaid nitrile compound comprises two nitrile official energy.

3, method according to claim 2 is characterized in that aforesaid nitrile compound is selected from methyl cellosolve acetate glutaronitrile, ethyl succinonitrile, adiponitrile and their mixture.

4,, it is characterized in that described hydroxyl basic cpd is selected from sodium hydroxide, potassium hydroxide according to each described method among the claim 1-3.

5, according to each described method in the aforesaid claim, it is characterized in that aforesaid hydroxyl basic cpd uses with aqueous solution form, preferably have the weight concentration of 5 to 30% basic cpd.

6, according to each described method in the aforesaid claim, the amount that it is characterized in that the hydroxyl basic cpd that uses is for according to 103% to 120% of the stoichiometric quantity of the basic cpd that amount calculated of nitrile compound to be transformed.

7,, it is characterized in that the being reflected at solvent refluxing between nitrile compound and the hydroxyl basic cpd carries out with adding to depress according to each described method in the aforesaid claim.

8,, it is characterized in that the reaction between nitrile compound and the hydroxyl basic cpd is carried out in discrete mode according to each described method in the aforesaid claim.

9,, it is characterized in that the reaction between nitrile compound and the hydroxyl basic cpd is implemented in a continuous manner according to each described method in the claim 1 to 7.

10, method according to claim 9 is characterized in that described being reflected at comprises that two are carried out continuously and in the equipment of the conversion zone that separates:

The first area is with whipped state work;

Second area is with piston mode work.

11, according to each described method in the aforesaid claim, the amount that the it is characterized in that employed mineral acid stoichiometric quantity that the hydroxyl basic cpd that adds is calculated that equals at least to be used to neutralize.

12,, it is characterized in that this mineral acid is selected from hydrochloric acid, sulfuric acid, has the organic acid that is less than or equal to 3 pKa and their mixture according to each described method in the aforesaid claim.

13,, it is characterized in that the extraction of the carboxylic compound of gained is undertaken by liquid/liquid extraction according to each described method in the aforesaid claim.

14, method according to claim 13 is characterized in that described liquid/liquid extraction is undertaken by the extraction solvent that use is selected from water-fast polar solvent.

15, method according to claim 14 is characterized in that described extraction solvent is selected from ketone, ether, ester.

16, method according to claim 15 is characterized in that described extraction solvent is selected from methyl iso-butyl ketone (MIBK), Di Iso Propyl Ether, methyl tertiary butyl ether, ethyl acetate, isopropyl acetate, butylacetate, diester.

17,, it is characterized in that the carboxylic compound that extracts separates with extraction solvent by distillation according to each described method in the aforesaid claim.

18, according to each described method in the aforesaid claim, the carboxylic compound that it is characterized in that being reclaimed is by distillation, crystallization, the refining purifying that carries out.

19,, it is characterized in that the carboxylic compound of this gained is converted to ester by the reaction with alcohol according to each described method in the claim 1 to 18.

20, method according to claim 19 is characterized in that described alcohol is selected from branching or non-branching, ring-type or acyclic Fatty Alcohol(C12-C14 and C12-C18), and it can contain aromatic ring and can contain 1 to 20 carbon atom.

21, method according to claim 20 is characterized in that described alcohol is selected from methyl alcohol, propyl alcohol, Virahol, phenylcarbinol, ethanol, propyl carbinol, isopropylcarbinol, hexalin, hexanol, isooctyl alcohol, 2-Ethylhexyl Alcohol, amylalcohol isomer, isopropylcarbinol.

22, according to each described method in the claim 19 to 21, it is characterized in that esterification is at H ⁺When existing, ion carries out.

23,, it is characterized in that this esterification carry out can be simultaneously removing in the reaction tower that anhydrates according to each described method in the claim 19 to 22.

24,, it is characterized in that described esterification undertaken by the ion-exchange sulfonic resin by the mixture that makes carboxylic compound/alcohol according to each described method in the claim 18 to 22.

25,, it is characterized in that the ester that generates reclaims and purifying by distillation according to each described method in the claim 18 to 24.